Multiplexing RTP and Data Channels over QUIC

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Table of Contents

1. Introduction

One of the requirements in the development of RTP over QUIC (RoQ) ([I-D.draft-ietf-avtcore-rtp-over-quic]) was the ability to share a QUIC connection for RTP, RTCP, and other protocols. RoQ uses a flow identifier to multiplex different RTP streams, RTCP, and possibly other protocols. However, RoQ does not describe which protocol can be multiplexed with RoQ on the same QUIC connection. [I-D.draft-engelbart-quic-data-channels] describes a simple protocol similar to WebRTC data channels ([RFC8831]) called QUIC Data Channels (QDC). QDC uses QUIC instead of SCTP over DTLS and also uses an identifier similar to the one used by RoQ. This document describes how the two protocols can be multiplexed in one QUIC connection.¶

2. Connection Establishment

QUIC requires the use of ALPN [RFC7301] during connection setup. Connections multiplexing RoQ and QDC use the "roq-qdc-mux" token during the TLS handshake.¶

3. Multiplexing

The two protocols for which this document describes a multiplexing scheme use a variable length integer as the first element on every QUIC stream and datagram. In RoQ, this integer is called a flow identifier, and it is used to multiplex different RTP streams and RTCP. In QDC, the integer is called a channel identifier and is used to multiplex multiple data channels.¶

This document describes two options for multiplexing RoQ and QDC. The first option builds upon the external signaling that is required by RoQ (Section 3.1). The second one works without any external signaling but places some restrictions on the chosen flow and channel identifiers (Section 3.2).¶

• TODO: If we define two methods, we also need to say how to choose between them. This could involve more external signaling, e.g., SDP, or we could use two different ALPNs. It might be easier to just settle on one single way to do it.¶

4. Error Handling

• TODO: This looks tricky. Some error codes will be easy to demultiplex when they are associated with a flow/channel ID. But some might not be, e.g., in CONNECTION_CLOSE frames.¶

5. Security Considerations

The security considerations for the QUIC protocol and datagram extension described in Section 21 of [RFC9000], Section 9 of [RFC9001], Section 8 of [RFC9002] and Section 6 of [RFC9221] apply.¶

6. IANA Considerations

Acknowledgments

Authors' Addresses